Flowering crab apple/apple rootstock `Geneva 65`

ABSTRACT

A new and unique apple rootstock `Geneva 65` that is very dwarfing and resistant to crown rot and fire blight. The tree is also useful as a small ornamental flowering crab.

BACKGROUND OF THE INVENTION

The present invention relates to a new and distinct cultivar of appletree, Geneva 65, which we discovered in a test planting belonging to NewYork State Agricultural Experiment Station, Cornell University,`Geneva`, Ontario County, N.Y. This discovery is a product of the applerootstock breeding program of the New York State Agricultural ExperimentStation (`Station`).

In 1974, pollen was collected from a Beauty Crab apple tree and used topollinate emasculated flowers of a Malling 27 (M.27) apple tree growingon Station grounds. The seeds were harvested from fruit produced fromthis cross and were stratified in November, 1974. After stratification,198 germinating seeds were planted in a Station greenhouse in January,1975. When the emerging seedlings were about 2.5 cm tall, we inoculatedthe soil with zoospores of 13 isolates of the fungus Phytophthoracactorum which is the causal agent of crown rot. The flat was flooded tomid-hypocotyl level of the seedlings, and kept at about 23° C. for 7days. All but 54 of the 198 seedlings were killed by this process. Thesurviving seedlings, when 10 to 15 cm tall, were inoculated in theirshoot tips with about 10⁶ cells of isolate Ea273 of the bacteriumErwinia amylovora, the causal agent of the of the fire blight disease,using a 26 -gauge hypodermic syringe. Four subsequent inoculations withE. amylovora isolate Ea273 were made.

We selected 5 Erwinia amylovora-resistant seedlings and planted them astrench layers on the Station's Loomis Farm in April, 1976. Rooted linerswere harvested in late fall 1979, 1980 and 1981 and were planted in theStation nursery in the springs of 1980, 1981 and 1982 respectively.Maiden trees of the cultivars `Northern Spy`, `Red Spy`, `GoldenDelicious`, `Topred Delicious`, `Summerland McIntosh` and `Mutsu` wereproduced by budding onto `Geneva 65` liners. These trees weresubsequently planted in trial orchards at the Station and at the UnitedStates Department of Agriculture Appalachian Fruit Research Station,Kearneysville, W.Va.; Hilltop Orchards, Hartford, Mich.; and HighmoorFarm, University of Maine, Monmouth, Me.

In these test plantings, trees on `Geneva 65` were about 20% smallerthan trees on the Malling 9 rootstock, based on comparison with thecheck trees in the same test plantings. Trees on `Geneva 65` beganflowering very early, usually the second year in the orchard; which wasespecially noteworthy for `Northern Spy` and `Red Spy` cultivars, whichat Geneva, N.Y., normally begin fruiting in the 5th or 6th year on theprecocity-inducing rootstock Malling-Merton 106. All of the cultivarsthat have been tested on `Geneva 65` have demonstrated high productionefficiency, equal to that experienced with the Malling 9 rootstock.

COMPATIBILITY

We have experienced no symptoms of incompatibility with 32 trees of the6 fruiting cultivars mentioned above. Besides these, we have grafted`Jonagold`, `Melrose`, `Empire` and `Liberty` cultivars on `Geneva 65`;in the nursery we have observed no symptoms of incompatibility. Allscionwood used was free from known harmful viruses. We have also grafted`Geneva 65` onto Novole and Malling-Merton 111 rootstocks to producemultiple stock trees with `Geneva 65` as interstems; we have observed noincompatibility symptoms.

PROPAGATION

We have propagated `Geneva 65` asexually by budding and grafting ontoseedling and clonal rootstocks; by root cuttings; by hardwood cuttings;by greenwood cuttings; by micropropagation; and by conventionallayering. These asexual propagules have remained true-to-type will allmethods of asexual propagation. We have also used `Geneva 65` as a seedparent in our breeding program; since `Geneva 65` is highlyheterozygous, its seedlings are much different from the maternal parentand from each other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows clusters of opened and unopened flowers of `Geneva 65`(G65).

FIG. 2 shows a single flower of `Geneva 65`.

FIG. 3 shows fruit of `Geneva 65`.

FIG. 4 shows a longisection of fruit of `Geneva 65`, showing typicalacuminate seeds.

FIG. 5 shows a two-year-old shoot of `Geneva 65`. Short spurry shootsare numerous on older wood and branches are few.

FIG. 6 shows leaves of `Geneva 65`, showing typical minute stipules,short petioles, cuspidate to nearly aristate tips, obtuse bases, andcoarsely serrate margins.

FIG. 7 show a two-year-old shoot of `Geneva 65`, showing lenticelsslightly raised, oval.

DESCRIPTION OF THE INVENTION

Following is a detailed description of our new cultivar `Geneva 65`Maluscv. Geneva 65. Accompanying figures depict flowering and fruiting habitand fruit characteristics, tree habit, and leaf and shootcharacteristics. The numerical color specifications employed are thoseof The Royal Horticultural Society Colour Chart (1976). Botanicaldescriptions follow Manual of Cultivated Plants (Bailey, 1949) andApples of New York (Beach, 1903).

FLOWERS AND FLOWERING

Flowers are borne on terminals of long shoots, on terminals of spurs,and from axillary buds of long shoots laid down the previous growingseason (FIG. 1). Typically, 7 flowers are produced from terminal buds,while 2 to 5 flowers are borne on axillary buds; the axillary buds withonly 2 or 3 flowers usually produce no vegetative shoots.

Flowers are single and very numerous. At full balloon state, the floweris red 48B, opening to white 155B and with red 49C on much of theabaxial surface. Structurally the flowers are typical of Malus, with a5-lobed calyx, 5 petals, 5 pistils, and about 20 stamens; each carpelusually has 2 ovules (FIG. 2). Flowers average about 22 mm diameter.Pedicels are short (25-30 mm) and stiff. Pollen is yellow-orange 15A,very abundant, germinates rapidly, and is long-lived in frozen storage.

FRUITING HABIT AND FRUIT

Flowers of `Geneva 65` are highly fertile, setting 50 to 100% of flowerspollinized with viable pollen. No "June drop" of fruit has beenobserved; fruits that have been fertilized are carried to maturity.Fruits are therefore borne in clusters of 2 to as many as 7 perpeduncle. A tree of `Geneva 65` that has carried an excessive cropproduced no or few flowers the following year.

The individual fruits are round to roundish oblate, symmetrical,regular, usually without residual calyx or retained stamens (FIGS. 3 and4). Fruits are about 20 mm diameter×18 mm long. Cavity is medium indepth and breadth, regular, often with light concentric russetting.Pedicels are short (25-30 mm), moderately thick and stiff. Lenticels onfruit are white, small, round, very slightly raised. Where exposed tosun, skin color is from red 38D to 48A on green-white 157C ground withlight bloom. Flesh is yellow-orange 23B; very firm; moderate texture;acid and astringent. Seeds are medium in size, 5.5 mm long×3.5 mm wide;usually 2 per carpel; dark brown; usually acuminate.

TREE HABIT

The unbudded tree of `Geneva 65` is a small shrub, typically standingabout 1.5 m tall × about 1 m wide. There is no single dominant trunk,but rather 15 to 30 shoots arising from the roots. The unbudded tree isa dwarf, comparable to a Malling 9 apple tree of similar age. Growthrate is slow, with very early cessation of growth typically occurringabout 2 weeks earlier than for Malling 9. Some suckers are produced butthe numbers are small and they are not exuberant.

SHOOTS

Adventitious shoots arising from roots, presumably juvenile, exhibitnumerous spines typically 3 to 7 or 8 cm long for the basipetal 10 to 20nodes; spines are uncommon on mature-phase shoots. In tissue culture,the most basipetal 1 or 2 leaves displayed on a new shoot may be deeplyincised, almost trilobate and similar in shape to Malus sargentii.

Matured shoots of current season are greyed-orange 175A; older shootsbecome darker brown to 166B. Shoots are quite short, usually less than20 cm, with short internodes, usually about 12-15 mm. Axillary buds areobtuse, sessile, usually somewhat appressed; most carry both vegetativeand flower primordia; bud scales moderately large, lightly tomentose.Lenticels are oval, medium in size, slightly raised, greyed-yellow 161Con new shoots. Burrknots are not commonly observed but do occuroccasionally on shoots 3 or more years old. No sphaeroblasts have beenobserved. Spring budbreak is midseason, after Novole, with Malling 9 andseveral days before Malling 26. Autumn leaffall is moderately early.Wood is not brittle as is that of Malling 9.

Timing of budbreak, blooming, maturing fruit and leaffall vary over arange of about 30 days at a given location and there is of course widevariation in related to climatic differences; therefore calendar datesfor these events would have no significance. The most usefuldescriptions are those which relate G.65 to a common standard, such asMalling 9. However, it should be noted that only budbreak and leaffallare likely to be useful, since flowers and fruit will rarely be observedon these plants.

Relative to Malling 9, budbreak of G.65 is similar ±2 days; full bloomof G.65 is usually 2 or 3 days earlier than M.9; fruit of G.65 maturesabout 45 days after M.9; in the nursery, cessation of active shootextension of G.65 is variable but 10 to 15 days before M.9; leaffall ofG.65 is similar to M.9 to a week later than M.9.

LEAVES

Lamella is ovate, tip cuspidate to nearly aristate, usually acuminate,margin is waxy; typically lamella for mature midshoot leaf will beapproximately 5 cm long and 2 cm wide leaf; margin coarsely serrate, 6to 8 serrations per cm; base obtuse, usually symmetrical, stipulesabsent or, rarely, minute. Adaxial lamella surface green 137A-B; abaxialsurface yellow-green 147C; both surfaces glabrous, dull, with a fewhairs on major veins. Petiole 15-20 mm long, slender. Leaf poisetypically 35°-40° from shoot.

USEFULNESS

`Geneva 65` is a very dwarfting rootstock for apples it is resistant tocrown rot and to fire blight, diseases that are limiting in many partsof the United States. In the orchard, anchorage of grafted trees issimilar to that of trees on Malling 26, but because of the precocityinduced by `Geneva 65` permanent support is strongly suggested.

`Geneva 65` also has promise as a disease-resistant interstem for apple.

Because the unbudded tree is a small, slow-growing shrub, `Geneva 65`can be used as an own-rooted ornamental flowering crab in locations inwhich resistance to fire blight is especially important.

We claim:
 1. A new and distinct cultivar of apple tree, substantially asshown and described herein, characterized particularly as to novelty bybeing a very dwarfing rootstock that is resistant to crown rot and tofire blight.